Reinforced flexible tubing and method of making same

Abstract

A method for making helically corrugated rubber tubing with a helical reinforcing element embedded therein and with a relatively smooth interior surface. The tubing is formed with separate inner and outer tubular wall portions with fabric material in between. The inner and outer wall portions may be formed of different elastomeric compositions. Also the method provides for annular cuffs at the opposite ends of the tubing.

What is claimed is: 
     
       1. A method for making a length of flexible, helically corrugated rubber tubing with a helical spring-like reinforcing element embedded therein comprising the steps of:
 sliding an uncured rubber inner sleeve over an assembly mandrel; 
 sliding a helical, spring-like reinforcing element over the inner sleeve, wherein the inner sleeve has end portions that extend axially beyond respective ends of the helical reinforcing element; 
 applying air pressure between the assembly mandrel and the inner sleeve to radially expand the inner sleeve into engagement with the surrounding reinforcing element; 
 placing a heat shrinkable fabric around the helical reinforcing element such that the fabric covers the helical reinforcing element but does not cover the end portions of the inner sleeve that extend axially beyond the respective ends of the helical reinforcing element; 
 applying sufficient heat to the fabric to shrink the fabric around and into tight engagement with the reinforcing element and the inner sleeve; 
 sliding an uncured rubber outer sleeve over the shrunken fabric, the helical reinforcing element and the uncured rubber inner sleeve to form a tubular assembly, wherein the outer sleeve includes end portions that extend axially beyond the respective ends of the helical reinforcing element; 
 rotating the tubular assembly about its axis while wrapping a cord about the outer sleeve to press portions of the outer sleeve into the spaces between adjacent convolutions of the reinforcing element; 
 heating the tubular assembly with the cord wrapped thereon to cure the inner and outer sleeves with the helical reinforcing element and fabric embedded therein to provide a cured length of rubber tubing; and 
 rotating the cured length of tubing about its axis in the reverse direction while unwrapping and removing the cord. 
 
     
     
       2. A method as defined in  claim 1  wherein the helical, spring-like reinforcing element is formed of metal. 
     
     
       3. A method as defined in  claim 2  wherein the helical, spring-like reinforcing element is formed of stainless steel. 
     
     
       4. A method as defined in  claim 1  wherein the heat shrinkable fabric comprises polyolefin weft yarns. 
     
     
       5. A method as defined in  claim 4  wherein the heat shrinkable fabric further comprises polyester warp yarns. 
     
     
       6. A method as defined in  claim 1  including, before the step of sliding the uncured rubber outer sleeve over the helical reinforcing element, the additional steps of:
 wrapping uncured rubber sheet material around at least one of the end portions of the inner sleeve in a plurality of layers to form a band; and 
 when the uncured rubber outer sleeve is slid over the helical reinforcing element, placing one of the respective axially extending end portions of the uncured rubber outer sleeve over the band. 
 
     
     
       7. A method as defined in  claim 1  wherein the uncured rubber inner sleeve and the uncured rubber outer sleeve are formed of different elastomeric compositions. 
     
     
       8. A length of reinforced helically corrugated rubber tubing made in accordance with the method of  claim 1 . 
     
     
       9. A method for making a length of flexible, helically corrugated rubber tubing with a helical spring-like metal reinforcing element embedded therein, comprising the steps of:
 sliding an uncured rubber inner sleeve over an assembly mandrel with a cylindrical outer surface; 
 sliding a helical, spring-like metal reinforcing element over the inner sleeve, wherein the inner sleeve has end portions that extend axially beyond respective ends of the helical reinforcing element; 
 applying air pressure between the assembly mandrel and the inner sleeve to radially expand the inner sleeve into engagement with the surrounding reinforcing element; 
 placing a heat shrinkable fabric around the helical reinforcing element such that the fabric covers the helical reinforcing element but does not cover the end portions of the inner sleeve that extend axially beyond the respective ends of the helical reinforcing element; 
 applying sufficient heat to the fabric to shrink the fabric around and into tight engagement with the reinforcing element and the inner sleeve; 
 wrapping uncured rubber sheet material around the opposite end portions of the inner sleeve in a plurality of layers to form bands; 
 sliding an uncured rubber outer sleeve over the shrunken fabric, the helical reinforcing element and the uncured rubber inner sleeve to form a tubular assembly; 
 placing oppositely extending end portions of the of the uncured rubber outer sleeve over the bands; 
 rotating the tubular assembly about its axis while wrapping a cord about the outer sleeve to press portions of the outer sleeve into the spaces between adjacent convolutions of the reinforcing element; 
 heating the tubular assembly with the cord wrapped thereon to cure the inner and outer sleeves with the helical reinforcing element and the fabric embedded therein to provide a cured length of rubber tubing and to cure the respective end portions of the inner and outer sleeves and the respective bands together to form end cuffs; and 
 rotating the rubber tubing about its axis in the reverse direction while unwrapping and removing the cord. 
 
     
     
       10. A method as defined in  claim 9  wherein the uncured rubber inner sleeve and the uncured rubber outer sleeve each have opposite end portions that extend axially beyond the opposite ends of the metal reinforcing element. 
     
     
       11. A method as defined in  claim 9  wherein the heat shrinkable fabric comprises polyolefin weft yarns. 
     
     
       12. A method as defined in  claim 11  wherein the heat shrinkable fabric further comprises polyester warp yarns. 
     
     
       13. A method as defined in  claim 9  wherein the uncured rubber inner sleeve and the uncured rubber outer sleeve are formed of different elastomeric compositions. 
     
     
       14. A method as defined in  claim 9  wherein the helical reinforcing element is formed of stainless steel.